A Long Term Evolution Hi (Long Term Evolution Hi, LTE Hi) architecture is a network architecture that is oriented to fixed and low-speed scenarios and relies upon existing mobile communications technologies. In the LTE Hi architecture, a user equipment (User Equipment, UE) initially establishes a primary carrier cell connection (Primary Carrier Cell, PCC) with a base station to connect to a core network. When a network traffic load increases to a limit value set by an operator, the base station configures a secondary carrier cell connection (Secondary Carrier Cell, SCC) for the UE through upper layer signaling and the UE is connected to the core network through an access node. User plane data and control plane data can be transmitted on the PCC, while only the user plane data can be transmitted on the SCC. The base station can transmit different UE services by hierarchy according to a quality of service (Quality of Service, QoS) requirement, an operator strategy, and the like. For example, a voice or video service with a relatively high quality of service requirement is transmitted on the PCC and a service with low additional values such as an a short message service is transmitted on the SCC. For a Uu interface on the PCC, context security protection is performed in an encryption and integrity protection manner on user plane data and/or control plane data transmitted over the Uu interface.
Although the Uu interface on the PCC is enabled with security protection, a Uu′ interface on the SCC is not enabled with security protection and thus transmission security of user plane data transmitted over the Uu′ interface cannot be ensured.